More than 50% of patients with ascending retrocecal appendicitis have an atypical clinical presentation. If the appendix is located retrocecally, it may give rise to an abscess in the pararenal space, or infection may spread along the right paracolic gutter up to the right posterior subhepatic and right subphrenic spaces. The clinical manifestations of acute appendicitis depend on the location of the appendix in the abdomen. If the appendix is in a retrocecal position, it may be positioned intraperitoneally in a paracecal pouch of peritoneum or retroperitoneally with or without a paracecal fossa formed by the peritoneum. The frequency of a retrocecal location ranges from 26% to 65%. If the cecum does not descend fully, the appendix becomes located retroperitoneally in an ascending retrocecal position anterior to the right kidney. The position of the appendix is determined mainly by changes in the position and shape of the cecum that occur during organ development, growth, and rotation. The anatomic location of the appendix varies among individuals. An abnormally long appendix (>7 to 10 cm) has been linked to the development of torsion, although this complication has also been reported for appendices of normal length. The appendix may exhibit a variety of anatomic abnormalities, including an atypical location, duplication, congenital absence, and luminal septal formation. Under normal circumstances, neutrophils and eosinophils are absent from the mucosa and wall of the appendix.Ĭongenital, Developmental, and Acquired Anatomic Abnormalities
The appendix is enveloped by serosa up to the point of attachment of the mesoappendix, where the serosa envelops the mesoappendiceal fat up to the peritoneal fold. The muscularis propria consists of an inner circular and outer longitudinal layer of smooth muscle, similar to other parts of the gastrointestinal (GI) tract. In addition to lymphoid tissue, abundant immunoglobulin A (IgA)–secreting plasma cells are normally present in the lamina propria. Unlike the colon, in which crypts are uniformly aligned, appendiceal crypts tend to be irregularly spaced and can be entirely absent in areas of mucosa adjacent to lymphoid aggregates. The epithelium of the appendix contains goblet cells, absorptive cells, neuroendocrine cells (predominantly Kulchitsky type and basally located), and scattered Paneth cells. It closely resembles mucosa from the terminal ileum, particularly in young individuals. However, the mucosa has abundant, organized lymphoid tissue circumferentially arranged. The layers of the appendix are similar to those in other portions of the large bowel, consisting of mucosa, submucosa, muscularis propria, and serosa.
#FIBROUS OBLITERATION OF APPENDIX FREE#
The appendiceal artery is derived from the ileocolic artery, which is derived from the superior mesenteric artery, and it is located at the free edge of the peritoneal fold.
The appendix is maintained in its position by a fold of peritoneum that invests mesoappendiceal fat throughout the length of the appendix. It may be located behind the cecum and ascending colon (most common location), behind the ileum and mesentery, along the pericolic gutter, in the subhepatic region, or in the lesser pelvis. It is approximately 8 cm long (range 2 to 20 cm) and 0.7 cm in diameter. The vermiform appendix arises from the medial aspect of the cecum, inferior and posterior to the ileocecal orifice. It has no proven significant physiologic function.
In humans, the appendix is a vestigial organ.
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